Materials Literature
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Results of structural and microanalytical studies on sintered iron rare-earth boron permanent magnets are presented in this paper. It is shown that the structure of the phase present at the two-grain boundaries is the same as that of the phase at the three-grain junctions; both are fcc with a lattice parameter of 5.24…
We prove that there are precisely three distinct icosahedrally symmetric lattices in three dimensions that are integral linear combinations of six vectors. By lattice, we mean a set of vectors which is closed under addition and subtraction. These three lattices can be represented as projections of the six-dimensional…
We have fabricated a macroscopically isotropic permanent magnet material (Ovonic Hi-RemTM) which significantly exceeds conventionally understood performance limits for a material with saturation magnetization Ms =16 kG. Enhanced magnetic properties, including a remanent magnetization Mr =9–10 kG or more, and a maximum…
We study the on-site model of a one-dimensional Fibonacci lattice. It is found that, compared with the transfer model, the electronic spectrum has different global structure, but the same branching rule in the following hierarchies. The relationship between the numbers of constructing elements of the lattice and the n…
A torque magnetometer used in a 100-kOe superconducting magnet was designed to measure magnetic anisotropy constants for hard magnetic materials with high magnetocrystalline anisotropy. This magnetometer consists of a pulley system and a motor driven shaft, on which strain gauges are pasted to detect the torque exerte…
Measurements of magnetic viscosity in Nd-Fe-B magnets of different kinds (sintered magnets, MQII magnets prepared from ribbons, and LDC magnets prepared by liquid dynamic compaction) are reported. In all magnets, the viscosity S and the irreversible susceptibility χirr are found to be proportional. The temperature dep…
Optical response of a sphere placed above a flat Ag substrate is calculated. Local dielectric constants are assumed and exact account is taken of the retardation effect. For a Ag sphere above a Ag substrate, coupling of sphere and substrate plasmons results in a strong local field, whereby Raman scattering by molecule…
Results on annealed nickel show that the total number of counts of both magnetic and acoustic Barkhausen signals vary inversely with grain size. In decarburized steels the total number of counts and the amplitude of both Barkhausen signals increase in proportion to grain size. The paper addresses these results in cont…
The electrical resistivity and the Seebeck coefficient of thermally evaporated thin bismuth films of thicknesses from 300 to 1900 A\r{} have been measured in the temperature range 300--470 K. The latter is negative and its magnitude is found to increase initially with increasing temperature, reach a maximum, and then…
We present the results of measurements of the inelastic scattering of X-rays with very high-energy resolution. Optical phonons in pyrolytic graphite with an energy transfer of Δ E = (171 ± 10) meV as well as an optical phonon in a Be single crystal with Δ E = (79 ± 10) meV were detected.
We present a detailed experimental study of ac-dc interference phenomena in charge-density-wave (CDW) transport. Harmonic and subharmonic ``steps'' of constant CDW current are observed when ac and dc voltages are applied together, and the widths of these steps exhibit Bessel-like oscillations as a function of both ac…
This corrosion study was performed to determine the reaction kinetics of Nd-Fe-B type magnets in oxidizing environments. Thus the oxidation model developed provides basic information for the development of oxidation-resistant magnets. The oxidation of Nd-Fe-B magnets was studied at temperatures between 20 and 150 °C.…
Reflectivity and Raman measurements of magnetite at 300, 130, 80, and 6 K are presented. The four infrared-active phonon modes and the five Raman modes exhibit fine structures below the Verwey transition (120 K), which are clearly detected for what may be the first time. A phenomenological analysis of the phonon spect…
A model is presented for the stress-dependent effective field, which when used in conjunction with the Jiles–Atherton theory, qualitatively accounts for (1) the change in slope and shape of the hysteresis curves with uniaxial stress and (2) the convexity of the curves depicting remanent and peak magnetization as a fun…
Magnetically isotropic Nd15Fe77B8 powder is prepared by mechanical alloying and a solid-state reaction from the elemental powders. Due to the extremely short reaction time (for example, 10 min at 700 °C) the magnetically isotropic particles have a very fine microstructure comparable to rapidly quenched samples, show a…
In rare earth (R)–transition metal (M) compounds, large R-M magnetic interactions can occur, which give rise to higher values of the ordering temperature (TC,TN) for compounds with magnetic R elements than for compounds with R nonmagnetic, i.e., La, Lu, Y. Due to the localized character of the 4f shell, these R-M inte…
The temperature dependence of the coercivity (HcI)of Nd15(Fe1−xCox)77B8 and (Nd1−xDyx)15Fe77B8 sintered magnets and that of the saturation magnetization (Ms) and the anisotropy field (HA) of Nd2(Fe1−xCox)14B and (Nd1−xDyx)2Fe14B single crystals have been observed in the temperature range between 295 and 800 K. The dep…
Dendritic growth of crystals in two dimensions is analyzed by a Green's-function method. A one-sided diffusional model is treated in quasistationary approximation. Anisotropy is found necessary for dendritic growth. We find scaling with anisotropy to be in agreement with recent results for needle crystals in the symme…
Submicron (<0.25 μm) wide lines of iron have been deposited by low-energy (0.5–3.0 keV) electron beam induced decomposition of iron pentacarbonyl. Selective area thermal decomposition of iron pentacarbonyl has also been demonstrated. It was found that under certain conditions, the thermal decomposition only occ…
First-principles, total-energy electronic structure calculations have been used to study the effects of charge transfer in graphite intercalation compounds. Together with an in situ diffraction study on graphite undergoing intercalation with sulphuric acid, the results strongly support the idea of a universal relation…